The data file below contains data on the weekly closing price of the S&P $500($a stock market index that tracks the performance of $500$ US companies and is commonly used as a measure of the US stock market$)$ for the year $2019.$

Note: This is a multiple answer question. This means one or more of the choices may be correct. You will receive partial credit for each correct answer. You will lose partial credit for each incorrectly selected answer $($this is merely to rule out selecting all answers as an optimal strategy$),$ so if you are not sure, it is better to leave the answer unchecked. For example, if there are two correct answers to a question and you only select one of them, you'll receive $50\%$ of the credit. If you select one correct and one incorrect option, you will receive no credit as the positive and negative partial credit cancel each other out. You overall score on the question however cannot be negative.

a$.$

linear trend

b$.$

simple exponential smoothing

c$.$

Holt's model

d$.$

random noise model